Implantable medical devices for reduced tissue inflammation

ABSTRACT

Implantable medical devices and methods for making and using the same are disclosed. An example implantable medical device may include a stent having a first configuration and a second expanded configuration. The stent may define a plurality of nodes. The stent may have a cover member disposed adjacent the nodes. The cover member may be configured to cover at least some of the nodes when the stent is in the expanded configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 14/190,343, filed Feb. 26, 2014, which claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 61/770,905, filed Feb. 28, 2013, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods for making and using medical devices. More particularly, the present disclosure pertains to implantable medical devices for reduced tissue inflammation.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. Some of these devices include guidewires, catheters, and the like. These devices are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. Of the known medical devices and methods, each has certain advantages and disadvantages. There is an ongoing need to provide alternative medical devices as well as alternative methods for manufacturing and using medical devices.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and use alternatives for medical devices. An example medical device may include an implantable medical device such as a stent. The stent may have a first configuration and a second expanded configuration. The stent may define a plurality of nodes. The stent may have a cover member disposed adjacent the plurality of nodes. The cover member may be configured to cover at least some of the plurality of nodes when the stent is in the expanded configuration.

Another example implantable stent may include a stent body having a plurality of nodes including a first node, a second node, and a third node. The second node may be positioned between the first node and the third node. A cover member may be attached to the first node and attached to the third node. The cover member may extend over and cover the second node.

An example method for reducing inflammation caused by a stent may include providing an implantable stent. The stent may comprise a stent body having a plurality of nodes including a first node, a second node, and a third node. The second node may be disposed between the first node and the third node. A cover member may be attached to the first node, may be attached to the third node, and may extend over the second node. The method may also include expanding the stent body and implanting the stent in a body lumen.

The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of an example implantable medical device disposed within a body lumen;

FIG. 2 is a side view of a portion of an example implantable medical device in a first configuration;

FIG. 3 is a side view of a portion of the example implantable medical device shown in FIG. 2 in a second configuration;

FIG. 4 is a side view of a portion of another example implantable medical device;

FIG. 5 is a side view of a portion of another example implantable medical device in a first configuration;

FIG. 6 is a side view of a portion of the example implantable medical device shown in FIG. 5 in a second configuration;

FIG. 7 is a side view of a portion of another example implantable medical device;

FIG. 8 is a side view of a portion of another example implantable medical device;

FIG. 9 is a side view of a portion of another example implantable medical device in a first configuration;

FIG. 10 is a side view of a portion of the example implantable medical device shown in FIG. 9 in a second configuration;

FIG. 11 is a side view of a portion of another example implantable medical device;

FIG. 12 is a side view of a portion of another example implantable medical device in a first configuration;

FIG. 13 is a side view of a portion of the example implantable medical device shown in FIG. 12 in a second configuration;

FIG. 14 is a side view of a portion of the example implantable medical device shown in FIG. 12 in a third configuration;

FIG. 15 is a side view of a portion of another example implantable medical device in a first configuration;

FIG. 16 is a side view of a portion of the example implantable medical device shown in FIG. 15 in a second configuration; and

FIG. 17 is a side view of a portion of another example implantable medical device.

While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include one or more particular features, structures, and/or characteristics. However, such recitations do not necessarily mean that all embodiments include the particular features, structures, and/or characteristics. Additionally, when particular features, structures, and/or characteristics are described in connection with one embodiment, it should be understood that such features, structures, and/or characteristics may also be used connection with other embodiments whether or not explicitly described unless clearly stated to the contrary.

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

The use of a stents, endoprostheses, implants, or the like may be a used to open or otherwise maintain the patency of the body lumen. For example, intravascular occlusions may be treated by implanting a stent within the blood vessel. Similarly, other body lumens including those along the digestive tract as well as along airways may also be treated in a similar manner. It can be appreciated that some body lumens may have a tendency to move. For example, peristalsis along portions of the digestive tract and/or along the esophagus may cause these body lumens to move. Similarly, the airways also move due to breathing, coughing, etc. A stent implanted along such regions could be subjected to forces that could cause the stent to elongate and/or shorten. This could lead to rubbing, pinching, poking, or general irritation at places where the stent and/or the relatively “sharp” edges of the stent contact the anatomy (e.g., along the mucous membrane or other tissues layer(s) in the lumen). In some cases, this could lead to inflammation, formation of granulation tissue, pain, or damage to the body lumen. Over an extended period of time, such irritation could lead to a number of different undesired consequences including reduced lumen patency, increased removal difficulty, greater mucus plugging, infection, or the like. Disclosed herein are example implantable devices such as stents that may help to reduce irritation, inflammation, or the like to body lumens. Such stents/implants may be well suited for implantation along body lumens that have a tendency to move or otherwise may be subjected to deformation forces.

FIG. 1 illustrates an example implant 10 disposed in a body lumen 12. In this example, implant 10 may take the form of a stent or endoprosthesis. In other embodiments, the structure and/or form of stent 10 may vary. In addition, body lumen 12 is shown schematically in this example and may represent the esophagus. This, however, is not intended to be limiting as body lumen 12 may represent a variety of different body lumens including those along the digest tract, along an airway, a blood vessel, etc. In some instances, body lumen 12 may be subjected to movement caused, for example, by peristalsis, breathing, coughing, or the like. When this happens, portions of stents like stent 10 may be expanded, shortened, or otherwise deformed. This could lead to rubbing, pinching, etc. of the anatomy, particularly along the ends or edges of the stent, which ultimately could cause inflammation and/or formation of granulation tissue. Stent 10 may include one or more structural features that help reduce inflammation and/or formation of granulation tissue. Some examples of the structural features that may be utilized to reduce inflammation and/or formation of granulation tissue are disclosed herein.

FIGS. 2-3 illustrate a portion of an example stent 110. In FIG. 2, stent 110 is shown in a first or “unexpanded” configuration. In FIG. 3, stent 110 is shown in a second or “expanded” configuration. Stent 110 may have a stent body or mesh-like structure 114. Accordingly, body 114 may have a generally cylindrical/tubular shape with a structure that resembles a braid, mesh, or matrix. It can be appreciated that for simplicity purposes, only a portion of body 114 is shown. Body 114 may define a plurality of stent edges or nodes defined therein such as nodes 116 a/116 b/116 c. The number of nodes 116 a/116 b/116 c may vary. In at least some embodiments, the number of nodes 116 a/116 b/116 c may vary depending on the shape, size/diameter, length, or other physical dimensions of body 114. In general, nodes 116 a/116 b/116 c may resemble points or pointed edges that may be disposed along the length of body 114. It can be appreciated, however, that a wide variety of shapes and/or configurations are contemplated for nodes 116 a/116 b/116 c. At least some of these shapes contemplated for nodes 116 a/116 b/116 c may be described as pointed, triangular, C-shaped, U-shaped, or the like. These are just examples.

A cover member 118 may be coupled to body 114. In general, cover member 118 may be configured to be disposed adjacent to one or more of nodes 116 a/116 b/116 c. Accordingly, cover member 118 may aid in blocking or shielding the anatomy from any somewhat “pointed” edges of nodes 116 a/116 b/116 c that may be present along body 114. For example, cover member 118 may be attached to node 116 a and to node 116 c. In at least some embodiments, cover member 118 may extend over node 116 b. Thus, cover member 118 may “cover” node 116 b, which may help reduce the likelihood of node 116 b pinching, poking, or otherwise irritating the anatomy. In addition, the attachment of cover member 118 to nodes 116 a/116 b may also help shield or otherwise reduce the likelihood of these nodes 116 a/116 b irritating the anatomy as well.

Forming stent 110 may include providing a tubular body and cutting the body into the desired configuration. This may include laser cutting the tube to define the stent body (e.g., body 114). For efficiency, for example, it may be desirable to cut the tubular body so as to define the stent body in a relatively “compact” or unexpanded configuration (e.g., similar to stent 110 and/or stent body 114 as shown in FIG. 2). In some embodiments, it may be desirable to expand or otherwise alter the shape of the stent prior to implanting. This may include disposing the stent onto a mandrel or suitable expanding structure to deform the stent body into a relatively “larger” or expanded configuration (e.g., similar to stent 110 and/or stent body 114 as shown in FIG. 3). When “expanded”, stent 110 may be delivered and implanted within the desirable portion of the anatomy.

FIG. 4 illustrates a portion of another example stent 210 that may be similar in form and function to other stents disclosed herein. Stent 210 may include stent body 214 and nodes 216 a/216 b/216 c. Cover member 218 may be coupled to body 214 much like cover member 118 is coupled to body 114. In some embodiments, one or more portions of body 214 may have an increased thickness relative to cover member 218. For example, body 214 may have a thickness T₁ (e.g., adjacent to one or more of nodes 216 a/216 b/216 c) that is thicker than the thickness T₂ of cover member 218. The increased thickness may help reduce the number of pointed or sharpened edges along body 214.

FIGS. 5-6 illustrate a portion of another example stent 310 that may be similar in is form and function to other stents disclosed herein. In FIG. 5, stent 310 is shown in a first or “unexpanded” configuration. In FIG. 6, stent 310 is shown in a second or “expanded” configuration. Stent 310 may have stent body 314. Body 314 may define nodes 316 a/316 b/316 c. Cover member 318 may be coupled to body 314. For example, cover member 318 may be attached to nodes 316 a/316 c and cover node 316 b. Body 314 may also include one or more radiopaque nodes 320 that may include a radiopaque material. Node 320 may have a loop formed thereon. In some instances, node 320 may be formed from a radiopaque material. In other instances, a radiopaque material may be disposed within the loop formed at node 320.

FIG. 7 illustrates a portion of another example stent 410 that may be similar in form and function to other stents disclosed herein. Stent 410 may include body 414 and nodes 416 a/416 b/416 c. Cover member 418 may include a node 422. In this example, node 422 may have a looped configuration much like node 320. In at least some embodiments, node 422 may include a radiopaque material.

FIG. 8 illustrates a portion of another example stent 510 that may be similar in form and function to other stents disclosed herein. Stent 510 may include body 514 and nodes 516 a/516 b/516 c. Cover member 518 may include a connector 524. Connector 524 may be attached to one of nodes 516 a/516 b/516 c such as node 516 b′. In general, connector 524 may help maintain the position of cover member 518 relative to body 514.

FIGS. 9-10 illustrate a portion of another example stent 610 that may be similar in form and function to other stents disclosed herein. In FIG. 9, stent 610 is shown in a first or “unexpanded” configuration. In FIG. 10, stent 610 is shown in a second or “expanded” configuration. Stent 610 may have stent body 614. Body 614 may define nodes 616. Cover member 618 may be coupled to body 614. In this example, rather than being a looped structure that extends between adjacent nodes, cover member 618 is formed at a position where a node may otherwise be defined. When stent 610 is expanded, cover member 618 may expand so as to cover adjacent nodes 616. Body 614 may also include one or more radiopaque nodes 620 that may include a radiopaque material.

FIG. 11 illustrates a portion of another example stent 710 that may be similar in form and function to other stents disclosed herein. Stent 710 may have stent body 714. Body 714 may define nodes 716. Cover member 718 may be coupled to body 714. In at least some embodiments, cover member 718 may be similar to cover member 618 but may have an alternative shape. For example, cover member 618 may have a rounded shape whereas cover member 718 may have a more oval shape. These embodiments illustrate that a variety of different shapes may be utilized for cover members 618/718. Body 714 may also include one or more radiopaque nodes 720 that may include a radiopaque material.

FIGS. 12-14 illustrate a portion of another example stent 810 that may be similar in form and function to other stents disclosed herein. In FIG. 12, stent 810 is shown in a first or “unexpanded” configuration. In FIG. 13, stent 810 is shown in a second or “expanded” configuration. In FIG. 14, stent 810 is shown in a third “expanded and formed” configuration.

Stent 810 may have stent body 814. Body 814 may define nodes 816. Cover member 818 may be coupled to body 814, for example at radiopaque node 820. However, in other embodiments cover member 818 may be coupled to body 814 at different locations. Cover member 818 may include a plurality of arms such as arms 818 a/818 b. Arms 818 a/818 b may be configured to be bent or otherwise formed into a configuration suited to cover one or more nodes 816. In some embodiments, arms 818 a/818 b may be formed using a forming mandrel or the like following the expansion of stent 810.

FIGS. 15-16 illustrate a portion of another example stent 910 that may be similar in form and function to other stents disclosed herein. In FIG. 15, stent 910 is shown in a first or “unexpanded” configuration. In FIG. 16, stent 910 is shown in a second or “expanded” configuration. Stent 910 may have stent body 914. Body 914 may define nodes 916. Cover member 918 may be coupled to body 914. For example, cover member 918 may be coupled to a node 916′. Cover member 918 may include a plurality of arms such as arms 918 a/918 b. Body 914 may also include one or more radiopaque nodes 920 that may include a radiopaque material.

FIG. 17 illustrates a portion of another example stent 1010 that may be similar in form and function to other stents disclosed herein. Stent 1010 may have stent body 1014. Body 1014 may define nodes 1016. Cover member 1018 may be coupled to body 1014. For example, cover member 1018 may be coupled to node 1016′. Cover member 1018 may include a plurality of arms such as arms 1018 a/1018 b. Body 1014 may also include one or more radiopaque nodes 1020 that may include a radiopaque material.

The materials that can be used for the various components of stent 110 (and/or other stents disclosed herein) may include those commonly associated with medical devices. For simplicity purposes, the following discussion makes reference to stent 110. However, this is not intended to limit the devices and methods described herein, as the discussion may be applied to other similar stents including those disclosed herein.

Stent 110 may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, ceramics, combinations thereof, and the like, or other suitable material. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material.

As alluded to herein, within the family of commercially available nickel-titanium or nitinol alloys, is a category designated “linear elastic” or “non-super-elastic” which, although may be similar in chemistry to conventional shape memory and super elastic varieties, may exhibit distinct and useful mechanical properties. Linear elastic and/or non-super-elastic nitinol may be distinguished from super elastic nitinol in that the linear elastic and/or non-super-elastic nitinol does not display a substantial “superelastic plateau” or “flag region” in its stress/strain curve like super elastic nitinol does. Instead, in the linear elastic and/or non-super-elastic nitinol, as recoverable strain increases, the stress continues to increase in a substantially linear, or a somewhat, but not necessarily entirely linear relationship until plastic deformation begins or at least in a relationship that is more linear that the super elastic plateau and/or flag region that may be seen with super elastic nitinol. Thus, for the purposes of this disclosure linear elastic and/or non-super-elastic nitinol may also be termed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may also be distinguishable from super elastic nitinol in that linear elastic and/or non-super-elastic nitinol may accept up to about 2-5% strain while remaining substantially elastic (e.g., before plastically deforming) whereas super elastic nitinol may accept up to about 8% strain before plastically deforming. Both of these materials can be distinguished from other linear elastic materials such as stainless steel (that can also can be distinguished based on its composition), which may accept only about 0.2 to 0.44 percent strain before plastically deforming.

In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy is an alloy that does not show any martensite/austenite phase changes that are detectable by differential scanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA) analysis over a large temperature range. For example, in some embodiments, there may be no martensite/austenite phase changes detectable by DSC and DMTA analysis in the range of about −60 degrees Celsius (° C.) to about 120° C. in the linear elastic and/or non-super-elastic nickel-titanium alloy. The mechanical bending properties of such material may therefore be generally inert to the effect of temperature over this very broad range of temperature. In some embodiments, the mechanical bending properties of the linear elastic and/or non-super-elastic nickel-titanium alloy at ambient or room temperature are substantially the same as the mechanical properties at body temperature, for example, in that they do not display a super-elastic plateau and/or flag region. In other words, across a broad temperature range, the linear elastic and/or non-super-elastic nickel-titanium alloy maintains its linear elastic and/or non-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy may be in the range of about 50 to about 60 weight percent nickel, with the remainder being essentially titanium. In some embodiments, the composition is in the range of about 54 to about 57 weight percent nickel. One example of a suitable nickel-titanium alloy is FHP-NT alloy commercially available from Furukawa Techno Material Co. of Kanagawa, Japan. Some examples of nickel titanium alloys are disclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which are incorporated herein by reference. Other suitable materials may include ULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available from Toyota). In some other embodiments, a superelastic alloy, for example a superelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions or all of stent 110 may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of stent 110 in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymer material loaded with a radiopaque filler, and the like.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI) compatibility is imparted into stent 110. For example, stent 110 may be made of a material that does not substantially distort the image and create substantial artifacts (i.e., gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. Stent 110 may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, and the like, and others.

It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement is of steps without exceeding the scope of the disclosure. This may include, to the extent that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments. The invention's scope is, of course, defined in the language in which the appended claims are expressed. 

What is claimed is:
 1. An implantable stent, comprising: a stent body having an unexpanded configuration and an expanded configuration; wherein the stent body includes a plurality of struts, wherein adjacent struts are joined together at nodes; wherein at least one of the nodes forms a cover member extending axially to a first end of the stent body, the cover member projecting laterally over adjacent nodes in the unexpanded configuration.
 2. The implantable stent of claim 1, wherein the stent body includes one or more radiopaque node loops, wherein each radiopaque node loop is attached to one of the nodes.
 3. The implantable stent of claim 2, wherein each radiopaque node loop is attached directly to one of the nodes.
 4. The implantable stent of claim 2, wherein the stent body includes a first radiopaque node loop and a second radiopaque node loop, and wherein the cover member is disposed between the first radiopaque node loop and the second radiopaque node loop.
 5. The implantable stent of claim 4, wherein the stent body further includes at least one additional node disposed between the first radiopaque node loop and the second radiopaque node loop.
 6. The implantable stent of claim 2, wherein each radiopaque node loop extends from its node axially toward the first end of the stent body.
 7. The implantable stent of claim 1, wherein in the expanded configuration, the cover member is disposed between adjacent nodes without overlapping the adjacent nodes.
 8. The implantable stent of claim 1, wherein the cover member has a rounded shape.
 9. The implantable stent of claim 1, wherein the cover member has an ovoid shape.
 10. An expandable stent, comprising: a stent body having a plurality of strut members joined at peaks and valleys formed by adjacent strut members; wherein the peaks of the stent body form a plurality of nodes including a first node, a second node, and a third node; wherein the second node forms a cover member attached to the plurality of strut members between the first node and the third node; wherein the cover member extends axially away from the peaks in a direction opposite the valleys.
 11. The expandable stent of claim 10, wherein the cover member is an enlarged loop directly attached to a first strut member and a second strut member at opposing ends of the cover member; wherein the cover member has a first portion extending in a first circumferential direction and a second portion extending in a second circumferential direction opposite the first circumferential direction; wherein in an unexpanded configuration of the expandable stent, the first portion extends circumferentially beyond the first node in the first direction and the second portion extends circumferentially beyond the third node in the second direction.
 12. The expandable stent of claim 11, wherein in an expanded configuration of the expandable stent, the first portion extends circumferentially beyond the first node in the first direction and the second portion extends circumferentially beyond the third node in the second direction.
 13. The expandable stent of claim 11, wherein in an expanded configuration of the expandable stent, the first portion does not extend circumferentially beyond the first node in the first direction and the second portion does not extend circumferentially beyond the third node in the second direction
 14. The expandable stent of claim 10, further comprising a plurality of radiopaque node loops extending from some of the peaks in the direction opposite the valleys.
 15. An expandable stent having a first end and a second end, comprising: a stent body having a plurality of strut members joined at peaks and valleys formed by adjacent strut members to define a plurality of stent sections extending circumferentially about the stent body; wherein successive peaks of each stent section form a plurality of nodes including a first node, a second node, a third node, a fourth node, and a fifth node; wherein the first node and the fifth node each include a radiopaque node loop extending therefrom toward the first end of the expandable stent; wherein the third node forms a cover member extending toward the first end of the expandable stent; wherein the cover member extends circumferentially over the second node and the fourth node in an unexpanded configuration.
 16. The expandable stent of claim 15, wherein the cover member extends further toward the first end of the expandable stent than the radiopaque node loops.
 17. The expandable stent of claim 15, wherein the fifth node of a first stent section forms the first node of an adjacent second stent section.
 18. The expandable stent of claim 15, wherein the cover member extends circumferentially over the second node and the fourth node in an expanded configuration.
 19. The expandable stent of claim 15, wherein the radiopaque node loops are spaced apart from the cover member.
 20. The expandable stent of claim 15, wherein the cover member extends circumferentially over the first node and the fifth node in the unexpanded configuration. 